Excess moisture, introduced by way of unsealed, vented crawlspaces, contributes to wood rot, mold growth and increased pest activity. Moisture in crawlspaces often migrates to the upper levels of the home through a "stack effect." In essence, whatever air is below the house is also in the house. As warm air rises and escapes through the upper levels of the home, new air finds its way into the home to replace what's been lost. Intake air comes in at the lower levels - through unsealed crawispaces. This may lead to costly problems such as cupping of hardwood floors, mold growth, increased air conditioner loads, and swelling of millwork/cabinetry. Air infiltration from the crawlspace often carries odors and may contribute to poor indoor air quality and uncomfortable humidity levels.
Excess moisture in crawlspaces has also been associated with contributing to increased energy consumption. Wintertime ventilation cools the crawlspace contributing to heat loss from the home. In the summer, introducing warm outside air under the home contributes to heat gains, increasing cooling loads. Ventilation of a crawlspace to control relative humidity only works consistently in an arid climate. In most climates, ventilation can actually add significant quantities of moisture during humid times.
Why Vented Crawlspaces Can Make Humidity Worse.
Venting a crawlspace will either add moisture to, or remove moisture from, a crawlspace depending on the moisture content of the ventilation air compared to the desired conditions of the crawlspace. Venting with dry air reduces moisture levels in the space, while venting with moist air contributes moisture. It is false to assume that venting will automatically bring in "good" air and push out the "bad" air. If the outside air is humid and the crawlspace air is humid, you're not making any improvements by venting. Since venting either wets or dries the space depending on outside conditions, there is no way to guarantee a specific moisture level in a vented crawlspace.
A Better Solution.
The solution to this dilemma is to close the crawlspace. One of the objectives of closing crawlspaces is to reduce sources of moisture entering the space. Even when done meticulously, closing a crawlspace will significantly reduce the moisture but not eliminate it. Active conditioning of the space may be necessary to maintain proper humidity levels. A dehumidifier can provide long-term, active moisture control and ensure humidity levels are maintained at a specific level which is adjustable by the home's occupant.
It is important to note the areas of concern when taking steps to responsibly convert your vented crawlspace to a sealed and conditioned space. Those include, but are not limited to: assuring proper water drainage, installing vapor barriers, consideration for combustion and carbon monoxide and sealing outside vents and controlling moisture with a Santa Fe crawlspace dehumidifier.
CONSEQUENCES OF HIGH HUMIDITY IN CRAWLSPACES
Wet crawlspaces contribute to the cupping of wood floors and the deterioration of floor joists, beams, sub-flooring, Insulation and electrical-mechanical systems.
Excess moisture encourages mold growth on wood and on any other organic material in a crawlspace.
Crawlspaces are a major source of air infiltration that permeates up into the living area, transmitting odors, carrying moisture, and creating an environment conducive to molds and dust mite infestation.
Because basement and crawispace floors and walls are in contact with the soil, and soil temperatures several feet below the surface remain at a constant temperature of 50°- 60°F, basement and crawlspace floors and walls tend to remain cool. Since basements and crawlspaces tend to be cool, and cool air holds less moisture than warm air, they will have higher relative humidity.
Typically, the closer to ground level, the larger the area, and the damper the environment, the more capacity that will be necessary to dry out the area. Capacity is usually measured in the number of pints of water that a dehumidifier can remove from the air at a given temperature over a given period of time.
Capacities for residential dehumidifiers are measured in pints of water removed per day at standard conditions. Standard conditions are determined by the American Home Appliance Manufacturers (AHA) and are used because capacity will vary with conditions. AHAM standard rating conditions are 80°F and 60% RH. The capacity of the Santa re Compact is 65 pints per day at these conditions.
The Santa Fe Compact is necessary to ensure that enough moisture is removed at the real-world temperature of your basement or crawlspace to prevent mold, mildew and bacterial growth. The Santa Fe Compact is a dehumidifier designed for these cooler applications.
Ventilation of a crawlspace to control relative humidity only works consistently in an arid climate. In most climates, ventilation can add significant quantities of moisture during humid times.
Depending on the outside weather, as much as 375 pounds of water per day can infiltrate a crawlspace through ventilation.
Proactive dehumidification of a sealed crawlspace is the only way to ensure desired humidity levels are present.
1. Seal all outside vents to eliminate outside air, which also reduces heating/cooling loads and uncontrolled moisture intake.
2. Install vapor barriers over exposed earth.
3. Condition crawlspace air with a Santa Fe Compact to provide humidity control regardless of outside conditions
Once your crawlspace has had a vapor barrier , de-humidifer, and encapsulation installation, you can expect to save up to 19% on your energy bill each month!
80% of the air in your house is affected by the quality of air in your home. So if there's mold, mildew, or rodent droppings in your crawlspace, expect the same type of quality to circulate through your home.
Ranging from 6mm-12mm we install what we find appropriate for your current crawlspace conditions.
Insects love warm & humid dark crawlspaces. Installing a vapor barrier greatly reducing the insect population of your crawlspace, which therefore reduces your insects that get in your home. It also provides a great surface for us to spray our pesticides on our bi-monthly plan to even further prevent bugs from entering your home..
Having a moist crawl-space is extremely conducive for wood mold & rot. Over time this mold & rot will destroy your home's lumber, and cause breathing problems for those who live there, especially those already with breathing. problems such as asthma. Installing a vapor barrier will keep the moisture in the ground below instead of in your home's wood and air.
Have one of our Bugno crawlspace professional inspect your crawlspace today to determine a game-plan based on your crawlspace condition and your current budget. We have a variety of options to decrease your crawlspace humidity, and can get a proposal sent to you within 48 hours of measuring and inspecting the crawlspace.
Too vent or not to vent crawls
Most of us, have been blissfully naïve. We thought that the "good air" would simply flow through the wall vents and that the "bad air" would be flushed out the same vents, thereby removing any dangerous moisture.
Much better than the typical crawl space encountered in the field, the wall-vented control houses in this study had well-installed insulation, 100 percent ground vapor retarder coverage of the soil and no problems with intrusion of liquid water from the outside.
Photo courtesy of Advanced Energy
For More Information
• Advanced Energy, www.crawlspaces.org
• Basement Systems Inc., www.basementsystems.com
• "Consider the Crawlspace," IBACOS,
• "Crawl Space Ventilation," Forest Products Laboratory,
• "Insulating Foundation and Floors," Southface Energy Institute,
What we didn't take into account were several other factors: moisture from the air as well as from the ground, the relationship between temperature and relative humidity, and "the stack effect," a natural phenomenon of constant movement of air through the house.
Here's how it works in crawl spaces: When hot air rises, most of it finds ways to escape into the upper areas of a house and then outside. As the hot air leaves the building, cool air rushes in through leaky windows, doors and crawl space vents to replace it and repeat the cycle. The air in the crawl space that gets sucked up into the living area brings with it moisture, dust, allergens, mold spores and radon. If the stack effect is causing air to be drawn into the house through the lower levels, then any possibility of meaningful cross-ventilation, allowing moist air to leave through the vents, is negated.
Should you eliminate vents from your additions and new construction?
What about ground covers or vapor retarders, usually 6-mil polyethylene, which most contractors use in conjunction with wall vents? After all, IRC Section R408.2, Exception 2 states, "The total area of ventilation openings may be reduced to 1/1,500 of the underfloor area where the ground surface is treated with an approved vapor retarder material and the required openings are placed so as to provide cross-ventilation of the space. The installation of operable louvers shall not be prohibited."
Yet even a ground cover can't make up for the moisture allowed into the home by wall vents in crawl spaces, according to the results of an ongoing research project co-funded by the U.S. Department of Energy and Advanced Energy, a research corporation in Raleigh, N.C. The study examines 12 Habitat for Humanity homes, identical but for their crawl spaces, built in 2001 in North Carolina.
Four homes have traditional wall-vented crawl spaces. The ground in these spaces was covered by 6-mil poly overlapped by 12 inches at all seams and secured with turf staples.
The foundation vents of the other eight homes were sealed. These crawl spaces have a sealed liner of 6-mil poly that extends up the foundation wall, stopping
3 inches from the top to provide a termite inspection gap. Turf staples secure the liner, and the seams are sealed with fiberglass mesh tape and mastic. The perimeter of the liner is secured with a furring strip nailed into the masonry and sealed with mastic. An HVAC supply duct provided 1 cubic foot per minute of conditioned air per 30 square feet of crawl space floor area whenever the air handler is running.
Advanced Energy found that the wall-vented crawl spaces stayed above 70 percent relative humidity during the summer, while the closed crawl spaces stayed below 60 percent. "Despite the carefully installed, 100 percent coverage ground poly, excess moisture continues to enter and remain in the wall vented crawl space," an April 2003 report concluded, pointing to humid outdoor air coming in through the events and rain and ground water wicking through the walls as the culprits.
The typical 6-mil polyethylene easily can be ripped by crawling on it, and the edges and seams are difficult to seal to the walls. Look for a heavy-duty, 10-mil to 20-mil, pool-liner type vinyl fabric with fiber reinforcement. The seams should be overlapped, sealed with a vinyl sealant and then covered with a vinyl, waterproof tape. I have tried several methods of securing the edges to the foundation wall. On most occasions, a 3/4-inch Ramset nail (with attached washer) shot in
2-foot intervals worked well to hold the fabric in place. I then came back and used the Bostik Chem-Calk 916 textured urethane sealant to bond the vinyl fabric to the masonry foundation wall..
The verdict is in, for the best air quality and least chance of mold growth, you must fully encapsulate your crawlspace.
Call today to get an estimate on your crawlspace encapsulation. Keep in mind this is not a normal vapor barrier installation. It requires much more material, work, and monitoring.
With WiFi ability sensors that hook up directly to the application (compatible for iPhones and Andriods).
with a 15 Mil Poly Plastic Vapor Barrier
Check out this great video on how a typical vapor barrier gets installed.
We're second to none when it comes to the installation of vapor barriers. Having a moisture level above 20% is conducive for mold and termite activity.
- First we clean out the crawlspace of all old barriers and debris.
- Then we install a 10-12mm poly plastic vapor barrier
- Wrap each pillar and seam them air tight from the ground.
- Close off all vents to block outdoor air & humidity from entering your crawlspace.
- Staple the barrier into the soil below to insure other's working in the crawlspace do not move the barrier.
- Finally we tape all the seams to provide a 100% ground coverage. Expect moisture levels to drop at least 10% within 6-8 months.
-We then do an annual inspection for any needed repairs or adjustments to keep the barrier intact and serve its purpose.
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Letting garbage like old duct work, pipes, wood, rodent droppings & urine, and other debris build up in your crawlspace will increase your insect activity dramatically and eventually end up inside your home.
Odors from your crawlspace will end up rising through your floorboards making your home's air quality deteriorate over time and affecting your family's respiratory systems.